I want to determine birth and death rate of a given phylogenetic tree using birthdeath of the ape package, and I get the following error:
birthdeath(phy)
Error in solve.default(out$hessian) :
Lapack routine dgesv: system is exactly singular: U[1,1] = 0
In addition: Warning messages:
1: In nlm(function(p) dev(p[1], p[2]), c(0.1, 0.2), hessian = TRUE) :
NA/Inf replaced by maximum positive value
2. etc...
The tree phy is ultrametric and appears to be fine, checkValidPhylo is true (in particular all edges have positive lengths). It plots just fine and looks normal...
I can upload the tree if need be.